U.S. Pat. No. 5,726,398 to Zahn et al. discloses a bumper/muffler assembly. A portion of the structure defining the muffler also forms part of the bumper and, hence, must be capable of absorbing high impact loads. If, after a certain period of vehicle operation, the muffler becomes defective and must be replaced, those defective parts must be replaced with costly parts capable of performing dual functions—attenuate acoustic energy and absorb high impact loads. The '398 patent also teaches that the bumper/muffler assembly may be formed from metal, see column 2, line 41. There are inherent limitations from a design standpoint regarding possible shapes and sizes for metal mufflers. Hence, the ability to design mufflers capable of being received in irregularly shaped vehicle recesses or cavities is restricted. It is also noted that the tooling costs for metal mufflers is very high, which is problematic where only a limited number of mufflers are to be produced, e.g., less than 100,000.
U.S. Pat. No. 6,543,577 discloses a silencer including a polymeric casing interconnecting an inlet pipe with an outlet pipe. A pair of heat resistant spacers in the form of bushings is located between an outer surface of the exhaust pipe and inner walls of the collars of the silencer. The bushings are formed of a heat resistant polymeric material and substantially seal the end of chamber 44 to provide resistance to heat transfer from the exhaust pipe to the casing from hot gases passing through the exhaust pipe. The bushings are flexible and soft relative to the casing and are capable of deforming to conform to irregularities in the shape of the exhaust pipe.
U.S. Pat. No. 5,340,952 discloses an exhaust muffler for an internal combustion engine formed of a synthetic resin material. An inner pipe is formed of a metallic material having a greater coefficient of thermal expansion than the muffler outer shell. Sliding movement may be allowed between a rear end of the sleeve member and inner pipe without breaking a substantially airtight engagement. A rear end of the sleeve member may be folded back inwardly and an annular member having a heat resistance and low coefficient of friction may be interposed between a folded back portion of the sleeve member and the rear end of the inner pipe so that they may slide over one another without excessive friction and transmission of heat from the inner pipe to the outer shell.
U.S. Pat. No. 4,045,057 illustrates a structure for interrupting the vibration along a pipeline or silencer shell, while structurally connection the parts together. The structure contains a series of spaced washer-shaped metal plates with vibration damping cushions, made of asbestos filled rubber, sandwiched between adjoining plates.
U.S. Pat. No. 4,880,078 discloses a muffler wherein the outlet end of the exhaust manifold is coupled to an upstream component unit through an elastomeric bushing. The bushing serves to dampen an exhaust vibration transmitted to the casing.
U.S. Pat. No. 4,993,513 illustrates a muffler having thermally resistant, heat insulation seals made of silicone rubber interposed between the outer ends of the attachment portions of the outer box of the muffler and the outer retainers of connecting members, which connect the muffler to the exhaust pipe. The seals also provide sound insulation.
U.S. Pat. No. 5,100,047 discloses a spacing ring that is placed between cooperating male and female tubular elements. The spacing rings provide space for expansion and contraction of the male and female elements and prevent direct contact between the elements to prevent undesirable noise. The spacing ring is made of matted threads or wires.
DE 4,326,304 illustrates a pipe-connecting element for the flexible connection of two pipes. The connecting element contains an annular band made of heat-shrinking plastic. The connecting element is fixed to the respective ends of the pipes and the annular band is melted to form a flexible connection between two pipes.
There is a need for an improved, low-cost composite muffler, which is capable of being associated with a vehicle bumper. Further, there is a need for a composite muffler associated with a vehicle bumper in which mechanical shock and vibration transmitted by the exhaust pipe of the muffler are reduced. Further, there is a need for a composite muffler associated with a vehicle bumper in which a thermal barrier between the exhaust pipe and shell of the composite muffler is provided to compensate for thermal expansion.